This invention relates to a technology for printing images on a print medium during main scanning, and particularly relates to a technology for correcting positional deviation of dots printed in a main scanning direction.
In recent years, color printers that emit ink of a plurality of colors from a head are coming into widespread use as computer output devices. In recent years, such color printers have been devised as multi-tone printers able to print a pixel using a plurality of types of dots having mutually differing sizes. Multi-tone printers use relatively small-volume ink droplets to form relatively small dots within a pixel area, and relatively large-volume ink droplets to form relatively large dots within a pixel area. Like other prior printers, such multi-tone printers can also perform so-called xe2x80x9cbi-directional printing,xe2x80x9d in order to increase the printing speed.
A problem that readily arises in bidirectional printing is that of deviation in printing position between forward and reverse printing passes in the main scanning direction, caused by backlash in the main scanning drive mechanism, and warping of the platen that supports the print medium from below, and the like. As a technology for resolving this positional deviation, for example, there is known that which is described in Patent Laid-open Gazette No. H05-69625, disclosed by the present applicants. With this prior technology, the amount of positional deviation (printing deviation) in the main scanning direction is registered beforehand, and this positional deviation amount is used as a basis for correcting the printing position during forward and reverse passes.
However, in addition to backlash in the main scanning drive mechanism and warping of the platen, print head characteristics have a major effect on positional deviation during bi-directional printing. That is, depending on the print head characteristics, dots formed by ink emitted from each nozzle may be subject to deviation in the main scanning direction. Conventionally, however, not much consideration had been given with respect to the effect that print head characteristics have on positional deviation arising during forward and reverse passes.
The above problem of positional deviation of dots in a main scanning direction is not limited to bi-directional printing, but also exists in unidirectional printing. In unidirectional printing, the problem becomes positional deviation between dots formed with different inks, or between dots formed with different rows of nozzles. Again, conventionally not much consideration had been given with respect to the effect that head characteristics have on positional deviation during unidirectional printing.
This invention was accomplished to resolve the above problems of the prior art, and has as its object to improve image quality by taking into consideration print head characteristics in alleviating positional deviation of dots in a main scanning direction.
For at least partially resolving the above problems, a first apparatus of this invention is a printing apparatus that prints on a print medium during main scanning, that includes a print head unit having a print head for printing dots at each pixel position on the print medium; a main scanning drive section that effects main scanning by moving at least one of the print medium and the print head unit; a sub-scanning drive section that effects sub-scanning by moving at least one of the print medium and the print head unit; a head drive section that applies drive signals to the print head to effect printing on the print medium; and a control section for controlling printing. The control section includes a printing position adjustment section that uses an adjustment value for reducing positional deviation of dots in a main scanning direction to adjust positioning of dots in a main scanning direction. Also, the print head unit is provided with readable head identification information that is set in accordance with characteristics relating to positional deviation of dots to be formed by the print head in a main scanning direction. The printing position adjustment section determines the adjustment value according to the head identification information.
In this way, adjustment value for correcting positional deviation are determined according to head identification information set in accordance with characteristics relating to positional deviation of the print head, so by taking print head characteristics into consideration, positional deviation of dots in a main scanning direction can be alleviated, improving image quality.
Moreover, the printing apparatus has a bidirectional printing function for printing in both the forward and reverse pass directions; and the printing position adjustment section may use the adjustment value to adjust the position of dots in the main scanning direction during bidirectional printing.
Also, the printing apparatus has a unidirectional printing function for printing during either one of forward pass and reverse pass; and the printing position adjustment section may use the adjustment value to adjust the position of dots in the main scanning direction during unidirectional printing.
In the above printing apparatus, the print head includes a plurality of nozzles; and a plurality of emission drive elements for emitting ink droplets from the plurality of respective nozzles; the plurality of emission drive elements may be divided into a plurality of groups. The head drive section can be provided with a base drive signal generator that generates a plurality of base drive signals corresponding to each of the plurality of groups; and a drive signal supply section that shape the plurality of base drive signals in response to given printing signals and supply the drive signals to the emission drive elements. At this time, it is preferable for the base drive signal generator to use the adjustment value supplied from the printing position adjustment section to output the plurality of base drive signals that have been individually phase adjusted.
In this way, by using a plurality of base drive signals corresponding to the plurality of groups that have been individually phase adjusted, it is possible to reduce on a group by group basis printing positional deviation caused by variations in the operating characteristics of the groups of emission drive elements.
In the above printing apparatus, the plurality of emission drive elements can be divided into groups corresponding to plural groups of emission drive elements, each group of emission drive elements corresponding to a plurality of nozzles arrayed in the sub-scanning direction.
This makes it possible to readily decrease positional deviation of dots in a main scanning direction.
In the above printing apparatus, also, the plurality of emission drive elements can be divided into groups according to type of ink emitted by the corresponding nozzles.
This makes it possible to decrease positional deviation of dots produced in a main scanning direction according to type of ink emitted from nozzles.
Also in the above printing apparatus, the printing position adjustment section preferably includes a first memory for storing a reference correction value for correcting printing positional deviation in a main scanning direction with respect to designated reference dots formed by the print head; a second memory for storing a relative correction value prepared beforehand for correcting the reference correction value; and an adjustment value determination section that determines the adjustment value by using the relative correction value to correct the reference correction value; with the relative correction value being determined in accordance with the head identification information.
Since, in this way, adjustment value for correcting positional deviation can be determined by using reference and relative correction values, it makes it possible to use printing modes adapted to various printing conditions to improve image quality by alleviating printing positional deviation in a main scanning direction.
Moreover, head identification information can be stored in non-volatile memory provided in the print head unit. Alternatively, head identification information can be displayed on an outer surface of the print head unit.
A second apparatus of this invention is a printing control apparatus that generates printing data to be supplied to a printing section that performs printing, the printing section including a print head unit having a print head for printing dots at each pixel position on the print medium; a main scanning drive section that effects main scanning by moving at least one of the print medium and the print head unit; a sub-scanning drive section that effects sub-scanning by moving at least one of the print medium and the print head unit; a head drive section that applies drive signals to the print head to effect printing on the print medium in response to given printing data; and a control section for controlling printing. The print head unit is provided with readable head identification information that is set in accordance with characteristics relating to positional deviation of dots formed in a main scanning direction by the print head. The printing control apparatus includes a printing data generation section that generates the printing data, which includes dot data representing dots to be formed at each pixel position on each main scanning line on the print medium, and adjustment data for adjusting, in pixel units, the printing position of dots to be formed in accordance with the dot data in a main scanning direction; and the printing data generation section includes an adjustment data determination section that determines the adjustment data to reduce positional deviation of dots in a main scanning direction in accordance with the head identification information.
Thus, positional deviation of dots in a main scanning direction can be alleviated and image quality improved also by generating and supplying to the printing section printing data that includes adjustment data determined in accordance with head identification information.
In the above printing control apparatus, the printing data can include, as the adjustment data, a prescribed number of adjustment pixel data corresponding to a prescribed number of pixels, and the adjustment data determination section can be arranged to distribute the prescribed number of adjustment pixel data to opposite ends of the dot data.
If the prescribed number of adjustment pixel data are thus distributed to opposite ends of the dot data, positional deviation of dots in a main scanning direction can be readily decreased. Moreover, distribution to opposite ends of the dot data is also meant to include a state in which all adjustment pixel data is distributed to either one end of the dot data, with no adjustment pixel data being distributed to the other end.
The recording medium of this invention is a computer-readable recording medium on which is recorded a computer program for generating printing data for a computer equipped with a printing apparatus that includes a print head unit having a print head for printing dots at each pixel position on the print medium; a main scanning drive section that effects main scanning by moving at least one of the print medium and the print head unit; a sub-scanning drive section that effects sub-scanning by moving at least one of the print medium and the print head unit; a head drive section that applies drive signals to the print head to effect printing on the print medium; a control section for controlling printing; the print head unit being provided with readable head identification information that is set in accordance with characteristics relating to positional deviation of dots to be formed by the print head in a main scanning direction; a computer-readable recording medium on which is recorded a function of generating the printing data that includes dot data representing dots to be formed at each pixel position on each main scanning line on the print medium, and adjustment data for adjusting, in pixel units, the printing position of dots to be formed in accordance with the dot data in a main scanning direction; and a function of determining the adjustment data to reduce positional deviation of dots in a main scanning direction in accordance with the head identification information.
Execution by a computer of the computer program recorded on the recording medium of this invention provides the same function and advantage as when a printing control apparatus of the invention is used, improving image quality by alleviating printing positional deviation in a main scanning direction.
A flexible disk, or CD-ROM, opto-magnetic disk, IC card, ROM cartridge, punched cards, printed material on which bar codes or other such symbols are printed, a computer internal storage device (memory such as RAM or ROM) as well as an external storage device and various other computer-readable media can be utilized as the xe2x80x9crecording mediumxe2x80x9d of this invention.
The present invention can be realized in various modes such as a printing apparatus, printing method, a printing control apparatus, printing control method, a computer program for realizing the functions of the apparatuses and methods thereof, a recording medium on which the computer program is recorded, data signals embodied in a carrier wave including the computer program, and so forth.